Shedding light on dark DNA Most textbook definitions of evolution state that it occurs in two stages: mutation followed by natural selection. DNA mutation is a common and continuous process, and occurs completely at random.
The average adult only eats 15 grams of fiber per day. Women need 25 grams of fiber per day, and men need 38 grams per day, according to the Institute of Medicine.
The recommendations: 1  Men aged 50 or younger should get 38 grams of fiber a day. 2  Women aged 50 or younger should get 25 grams of fiber a day.  Because we need fewer calories and food as we get older, men over aged 50 should get 30 grams of fiber a day.